When a thermoplastic container, cup, or similar product is filled with a hot product, typically a liquid or a slurry, and then sealed, the contents reduces in volume as it cools. The hot gas in the cup cools, resulting in a vacuum inside the cup and deformation to the sidewalls, often referred to in the art as paneling. To understand this phenomenon more clearly, consider that a liquid container has part liquid product and part gas content therein. If, after sealing, the original mass of gas at the time the container is sealed contracts in volume, as would be the case with a decrease in temperature, it accordingly creates a vacuum. This vacuum in the container can collapse, or partially collapse the sidewalls, resulting in paneling.
Paneling is particularly a problem where the walls of the cup are thin, or otherwise not sufficiently rigid to prevent the collapse or deformation of the walls. This is increasingly the case as manufacturing targets require minimal use of material or where the aim is to reduce the overall weight of the container. Paneling results in a number of possible problems, including altering the appearance of the container to the point that consumers may not purchase or would otherwise return to a point of purchase a product in a container with collapsed sidewalls. Furthermore, where such containers are to be stacked on store shelves, for example, paneling may having a negative impact on the stackability of the containers.
As is known in the art, it is possible to mitigate some of the effects of paneling by designing containers with thicker walls, or having other strengthening elements within the container. However, these solutions are not always possible or can lead to increased material costs, container weight and other manufacturing and/or design inefficiencies. This is particularly the case as where manufacturing capabilities are able to produce thinner walled containers than has been possible in the past.
Accordingly, there is a need in the art for an improved container that mitigates one or more of the above identified problems in the prior art.